For the upcoming year, the nation's second-largest school system has amped up the number of campus security aides monitoring elementary schools, funneling $4.2 million into 1,000 new positions, officials said.

Most of those positions have been filled, said Steve Zipperman, chief of the district's police department.

Schools across Southern California have also taken additional safety precautions with increased security, surveillance cameras, revised lockdown measures and fewer open gates.

Some schools have taken more visible steps to protect campuses. At Monterey Highlands Elementary in Monterey Park, a nearly finished wrought-iron fence now stands around the school's perimeter.

On Thursday, the first day of school, staff members will be stationed before and after school at three main access points.

Until this summer, Monterey Highlands, a K-8 school with about 880 students nestled in the hillside of a quiet residential neighborhood, was the only school without a fence in the Alhambra Unified School District.

In the last decade, administrators, teachers and parents have debated whether to build one, but last winter, shaken district leaders pointed to Newtown and similar incidents and declared that a fence at Monterey Highlands was a priority.

The fence cost the district about $226,200 in construction bonds.

Sandy Hook wasn't the only red flag, officials said. Last fall, a man caused a disturbance when he entered several classrooms, leading administrators to call police.

"We just felt it was time," said Alhambra Unified Supt. Laura Tellez-Gagliano.